Various classes of graphical models describe computations that can be performed on computational hardware, such as a computer, microcontroller, FPGA, and custom hardware. Classes of such graphical models include time-based block diagrams such as those found within Simulink® from The MathWorks, Inc. of Natick, Mass., state-based and flow diagrams, such as those found within Stateflow® from The MathWorks, Inc. of Natick, Mass., data-flow diagrams, circuit diagrams, and software diagrams, such as those found in the Unified Modeling Language. A common characteristic among these various forms of graphical models is that they define semantics on how to execute the diagram.
Historically, engineers and scientists have utilized graphical models in numerous scientific areas such as Feedback Control Theory and Signal Processing to study, design, debug, and refine dynamic systems. Dynamic systems, which are characterized by the fact that their behaviors change over time, or the fact that their states change or the fact that their behaviors change due to a system environment, are representative of many real-world systems. Graphical modeling has become particularly attractive over the last few years with the advent of software packages such as Simulink® from The MathWorks, Inc. of Natick, Mass. Such packages provide sophisticated software platforms with a rich suite of support tools that makes the analysis and design of dynamic systems efficient, methodical, and cost-effective.
A dynamic system, either natural or man-made, is a system whose response at any given time is a function of its input stimuli, its current state, the current time, and other input parameters. Such systems range from simple to highly complex systems. Physical dynamic systems include a falling body, the rotation of the earth, bio-mechanical systems (muscles, joints, etc.), bio-chemical systems (gene expression, protein pathways), weather and climate pattern systems, etc. Examples of man-made or engineered dynamic systems include: a bouncing ball, a spring with a mass tied on an end, automobiles, airplanes, control systems in major appliances, communication networks, audio signal processing, nuclear reactors, a stock market, etc. Professionals from diverse areas such as engineering, science, education, and economics build graphical models of dynamic systems in order to better understand system behavior as it changes with the progression of time. The graphical models aid in building “better” systems, where “better” may be defined in terms of a variety of performance measures such as quality, time-to-market, cost, speed, size, power consumption, robustness, etc. The graphical models also aid in analyzing, debugging and repairing existing systems (be it the human body or the anti-lock braking system in a car). The models may also serve an educational purpose of educating others on the basic principles governing physical systems. The models and results are often used as a scientific communication medium between humans. The term “model-based design” is used to refer to the use of graphical models in the development, analysis, and validation of dynamic systems.
Graphical modeling environments such as Simulink®, assist in simplifying the process of designing, simulating, and implementing dynamic systems. A graphical model is a representation of a real-world system through a graph containing nodes (i.e. blocks) interconnected by arcs (i.e. lines). Blocks are functional entities that perform mathematical operations, transformations or both on the data and information being processed by the system. The lines, often referred to as signals in the art, represent streams of information, such as data, data types, timing information, and control information, flowing into, out of, and between various blocks.
Signals in current graphical model environments have a number of associated attributes, such as dimensions and data type. Blocks that operate on such signals expect that attributes to be of given pre-defined data types. In order to handle a custom data type for such an attribute, the code for the blocks would have to be rewritten. As a result, the blocks are somewhat inflexible in their handling of such data types for attributes of signals.